Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.33	9.501%	$123.0025	$123.00	$123.00	$123.00
Purchase #2	$117.40	11.545%	$130.9538	$130.95	$130.95	$131.00
Purchase #3	$56.35	5.840%	$59.6408	$59.64	$59.65	$59.60
Purchase #4	$40.67	7.124%	$43.5673	$43.57	$43.55	$43.60
Purchase #5	$91.86	10.716%	$101.7037	$101.70	$101.70	$101.70
Purchase #6	$27.38	3.267%	$28.2745	$28.27	$28.25	$28.30
Purchase #7	$186.94	12.573%	$210.444	$210.44	$210.45	$210.40
7 purchase totals =	$632.93		$697.5866	$697.57	$697.55	$697.60